c
If effective resistance is $x$,
$\Rightarrow x=1+\frac{x \times 1}{x+1}+1$
$\Rightarrow(x-2)=\frac{x}{x+1}$
$\Rightarrow x^2-x-2=x$
$\Rightarrow x^2-2 x-2=0$
$\text { So, } x=\frac{2 \pm \sqrt{12}}{2}$
$=1 \pm \sqrt{3}\,\Omega$
neglecting negative value, $x =1+\sqrt{3}\,\Omega$
